Framework modification

The high silica zeolites with Si/Al of 10-100 can be generated by either thermochemical framework modification of hydrophilic zeolites or by direct synthesis. In... 

Ion-exchange, framework modification, and secondary synthesis of microporous and porous materials ... 

Nearly all syntheses of zeolites and microporous aluminophosphates have limitations to gel composition and other parameters. For example, some zeolites with special compositions such as high-silica Y zeolite and low-silica ZSM-5 cannot be directly synthesized. A secondary framework modification is necessary for their preparation. For instance, dealuminization, isomorphous substitution of extraneous silicon for aluminum, and removal of the sodium process in Y zeolite are necessary to prepare ultra-stable zeolite Y (USY) isomorphous replacement of framework atoms of boron with aluminum in a presynthesized silicon-boron structure is often used to prepare some specific aluminosilicate zeolites that cannot be directly synthesized, such as Al-SSZ-24 (AFI) and Al-CIT-1. Secondary synthesis (post-treatment) will be discussed in detail in Chapter 6. 

Framework Modifications of [60]Fullerene Cluster Opening Reactions and Synthesis of Heterofullerenes... 

Here, a first review is provided which summarizes the more recent development framework modified fullerenes like cluster opened structures and heterofullerenes. The key steps for such framework modifications are always defined activations of the fullerene cluster due to specific covalent addition reactions. Therefore, the principles of covalent fullerene chemistry [3-8] will be considered first ... 

Formed by chemical framework modification (dealumination) the Al is partially removed by treatment with steam or SiCU at high temperatures. 

Pre designed framework modification of porous polymers and the insertion of functionalization can be facilitated by pre- or post-synthetic... 

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